1. Field of the Invention
The present invention relates to a blast fan for blowing air in a centrifugal direction thereof, and more particularly to a blast fan having a plurality of turbo blades, each integrally installed to the tip or trailing edge of a rotary blade, for achieving an increase in the flow rate and a significant reduction in noise generated.
2. Description of the Related Art
In general, a blast fan is mounted to home electronics including refrigerators, air conditioners, microwave ovens and so on, and adapted to blow air while being rotated by a motor.
FIG. 1 is a front view showing the construction of a conventional axial flow fan, FIG. 2 is a side view of the conventional axial flow fan, and FIG. 3 is a sectional view showing the construction of a refrigerator equipped with the conventional axial flow fan.
The conventional axial flow fan, as shown in FIGS. 1 and 2, comprises a hub 2 coupled to a rotating shaft of a motor (not shown) and adapted to be rotated by the motor, and a plurality of rotary blades 4 equally spaced and arranged around the outer peripheral surface of the hub 2 for blowing air.
The axial flow fan 10, configured as stated above, is used in various electric units including refrigerators, air-conditioners, microwave ovens and so on. Now, a general operation of a refrigerator including the conventional axial flow fan will be described.
As shown in FIG. 3, the axial flow fan 10 is mounted within a flow channel, formed along one side of a freezing compartment F and refrigerating compartment R, and connected with a motor 12. The axial flow fan 10 serves to blow cooled air, passing through an evaporator 14 located at the bottom side of the freezing compartment F, toward the freezing compartment F or refrigerating compartment R.
In detail, as a compressor 16 and the axial flow fan 10 are operated, a coolant is circulated through the compressor 16, a condenser 18, a capillary tube (not shown) and the evaporator 14. During circulation, heat exchange takes place in the evaporator 14 to allow the coolant to provide the cooled air, which is subsequently supplied into the freezing compartment F and refrigerating compartment R by means of the axial flow fan 10, to thereby cool any food stored in the freezing compartment F or refrigerating compartment R.
The cooled air is circulated along the flow channel extending from the freezing compartment F to refrigerating compartment R, so that it exhibits a high air flow resistance against the flow channel. Due to this high air flow resistance, the axial flow fan 10, generally used in the refrigerator, has a relatively large size and must be rotated at a high speed.
These problems of the conventional axial flow fan 10 occur in other electric units including air-conditioners and microwave ovens as well as refrigerators. In conclusion, the high air flow resistance of the flow channel increases the size and rotation speed of the axial flow fan 10.
When the axial flow fan 10 is mounted in the flow channel exhibiting the high air flow resistance, the flow rate of the fan is reduced due to the high air flow resistance. Also, since the motor 12 has to be rotated at a high speed, the level of noise generated from the fan is increased.
Although a turbo fan, adapted to forcibly propel air, is applied to solve a high air flow resistance problem as stated above, it is still not sufficient to ensure a high flow rate.
Where the blast fan is a kind of low static pressure and high flow rate type axial flow fan, which is adapted to achieve a wide range of flow rates in accordance with a pressure variation, the flow rate of the fan is reduced and the level of noise generated is increased according to an increase in air flow resistance. Where the conventional blast fan is a kind of high static pressure and low flow rate type turbo fan, which is advantageously used under the high air flow resistance condition, it still fails to blow a large amount of air.